Ejectors and Methods of Use

ABSTRACT

An ejector has: a motive flow inlet ( 40 ); a secondary flow inlet ( 42 ); an outlet ( 44 ); a motive flow nozzle ( 242 ) having an outlet ( 110 ); a primary flowpath from the motive flow inlet through the motive flow nozzle to the ejector outlet; a secondary flowpath from the secondary flow inlet to the ejector outlet, merging with the primary flowpath at the motive nozzle outlet; a control needle ( 200; 300; 400 ) shiftable along a range of motion between a first condition and a second condition and seated against the motive nozzle in the second condition. The needle comprises: a main shaft ( 210 ); a tip ( 204 ); a first portion ( 220; 320 ) converging toward the tip; and a shoulder portion ( 214; 314; 422 ) between the first portion and the main shaft and seated against the motive nozzle in the second condition and converging toward the tip at a greater angle ( ?1; ?1 2 ) than an angle ( ?2; ?2 2 ) of the first portion.

CROSS-REFERENCE TO RELATED APPLICATION

Benefit is claimed of U.S. Patent Application Ser. No. 61/933,777, filedJan. 30, 2014, and entitled “Ejectors and Methods of Use”, thedisclosure of which is incorporated by reference herein in its entiretyas if set forth at length.

BACKGROUND

The present disclosure relates to refrigeration. More particularly, itrelates to ejector refrigeration systems.

Earlier proposals for ejector refrigeration systems are found in U.S.Pat. Nos. 1,836,318 and 3,277,660. FIG. 1 shows one basic example of anejector refrigeration system 20. The system includes a compressor 22having an inlet (suction port) 24 and an outlet (discharge port) 26. Thecompressor and other system components are positioned along arefrigerant circuit or flowpath 27 and connected via various conduits(lines). A discharge line 28 extends from the outlet 26 to the inlet 32of a heat exchanger (a heat rejection heat exchanger in a normal mode ofsystem operation (e.g., a condenser or gas cooler)) 30. A line 36extends from the outlet 34 of the heat rejection heat exchanger 30 to aprimary inlet (liquid or supercritical or two-phase inlet) 40 of anejector 38. The ejector 38 also has a secondary inlet (saturated orsuperheated vapor or two-phase inlet) 42 and an outlet 44. A line 46extends from the ejector outlet 44 to an inlet 50 of a separator 48. Theseparator has a liquid outlet 52 and a gas outlet 54. A suction line 56extends from the gas outlet 54 to the compressor suction port 24. Thelines 28, 36, 46, 56, and components therebetween define a primary loop60 of the refrigerant circuit 27. A secondary loop 62 of the refrigerantcircuit 27 includes a heat exchanger 64 (in a normal operational modebeing a heat absorption heat exchanger (e.g., evaporator)). Theevaporator 64 includes an inlet 66 and an outlet 68 along the secondaryloop 62. An expansion device 70 is positioned in a line 72 which extendsbetween the separator liquid outlet 52 and the evaporator inlet 66. Anejector secondary inlet line 74 extends from the evaporator outlet 68 tothe ejector secondary inlet 42.

In the normal mode of operation, gaseous refrigerant is drawn by thecompressor 22 through the suction line 56 and inlet 24 and compressedand discharged from the discharge port 26 into the discharge line 28. Inthe heat rejection heat exchanger, the refrigerant loses/rejects heat toa heat transfer fluid (e.g., fan-forced air or water or other fluid).Cooled refrigerant exits the heat rejection heat exchanger via theoutlet 34 and enters the ejector primary inlet 40 via the line 36.

The exemplary ejector 38 (generically shown in FIG. 2) is formed as thecombination of a motive (primary) nozzle 100 nested within an outermember 102. The primary inlet 40 is the inlet to the motive nozzle 100.The outlet 44 is the outlet of the outer member 102. The primaryrefrigerant flow 103 enters the inlet 40 and then passes into aconvergent section 104 of the motive nozzle 100. It then passes througha throat section 106 and an expansion (divergent) section 108 through anoutlet (exit) 110 of the motive nozzle 100. The motive nozzle 100accelerates the flow 103 and decreases the pressure of the flow. Thesecondary inlet 42 forms an inlet of the outer member 102. The pressurereduction caused to the primary flow by the motive nozzle helps draw thesecondary flow 112 into the outer member. The outer member includes amixer having a convergent section 114 and an elongate throat or mixingsection 116. The outer member also has a divergent section or diffuser118 downstream of the elongate throat or mixing section 116. The motivenozzle outlet 110 is positioned within the convergent section 114. Asthe flow 103 exits the outlet 110, it begins to mix with the flow 112with further mixing occurring through the mixing section 116 whichprovides a mixing zone. Thus, respective primary and secondary flowpathsextend from the primary inlet and secondary inlet to the outlet, mergingat the exit. In operation, the primary flow 103 may typically besupercritical upon entering the ejector and subcritical upon exiting themotive nozzle. The secondary flow 112 is gaseous (or a mixture of gaswith a smaller amount of liquid) upon entering the secondary inlet port42. The resulting combined flow 120 is a liquid/vapor mixture anddecelerates and recovers pressure in the diffuser 118 while remaining amixture. Upon entering the separator, the flow 120 is separated backinto the flows 103 and 112. The flow 103 passes as a gas through thecompressor suction line as discussed above. The flow 112 passes as aliquid to the expansion valve 70. The flow 112 may be expanded by thevalve 70 (e.g., to a low quality (two-phase with small amount of vapor))and passed to the evaporator 64. Within the evaporator 64, therefrigerant absorbs heat from a heat transfer fluid (e.g., from afan-forced air flow or water or other liquid) and is discharged from theoutlet 68 to the line 74 as the aforementioned gas.

Use of an ejector serves to recover pressure/work. Work recovered fromthe expansion process is used to compress the gaseous refrigerant priorto entering the compressor. Accordingly, the pressure ratio of thecompressor (and thus the power consumption) may be reduced for a givendesired evaporator pressure. The quality of refrigerant entering theevaporator may also be reduced. Thus, the refrigeration effect per unitmass flow may be increased (relative to the non-ejector system). Thedistribution of fluid entering the evaporator is improved (therebyimproving evaporator performance). Because the evaporator does notdirectly feed the compressor, the evaporator is not required to producesuperheated refrigerant outflow. The use of an ejector cycle may thusallow reduction or elimination of the superheated zone of theevaporator. This may allow the evaporator to operate in a two-phasestate which provides a higher heat transfer performance (e.g.,facilitating reduction in the evaporator size for a given capability).

FIG. 2 shows controllability provided by a needle valve 130 having aneedle 132 and an actuator 134. The actuator 134 shifts a tip portion136 of the needle into and out of the throat section 106 of the motivenozzle 100 to modulate flow through the motive nozzle and, in turn, theejector overall. Exemplary actuators 134 are electric (e.g., solenoid orthe like). The actuator 134 may be coupled to and controlled by acontroller 140 which may receive user inputs from an input device 142(e.g., switches, keyboard, or the like) and sensors (not shown). Thecontroller 140 may be coupled to the actuator and other controllablesystem components (e.g., valves, the compressor motor, and the like) viacontrol lines 144 (e.g., hardwired or wireless communication paths). Thecontroller may include one or more: processors; memory (e.g., forstoring program information for execution by the processor to performthe operational methods and for storing data used or generated by theprogram(s)); and hardware interface devices (e.g., ports) forinterfacing with input/output devices and controllable systemcomponents.

The FIG. 1 embodiment also shows bypass lines 80 and 82 for operating ina second mode wherein flow through the ejector is shut off. The bypassline 80 bypasses the ejector and allows refrigerant to pass from theheat rejection heat exchanger 30 to the separator without passingthrough the ejector. The bypass line 82 allows refrigerant to pass fromthe heat absorption heat exchanger 64 back to the compressor. Thus, thesecond mode represents a basic non-ejector vapor compression system. Toenter the second mode, the system may include valves (e.g., on-offsolenoid valves) 84, 86, 88, and 90. The valves 84 and 86 arerespectively in the lines 80 and 82 and, in the first mode, areoff/shut/closed. The valve 88 is in the line 36 downstream of thejunction between the bypass line 80 and the ejector inlet so as to beable to close off ejector motive flow only. The valve 90 is in the line72 downstream of where the bypass 82 intersects. The valves 88 and 90are open in the first mode. The states of the valves are reversedbetween the first mode and the second mode.

In yet further variations, additional expansion devices and heatexchangers may be added. In one example, an economizer heat exchanger 94has a first leg 96 along the line 72 upstream of the expansion device 70and a second leg 98 along the line 56 from the vapor outlet 54 upstreamof the junction with the bypass 82. An expansion device 92 may beupstream of the second leg. An expansion valve 99 is also showndownstream of the heat rejection heat exchanger. Valve 92 is used toprovide further cooling (sub-cooling) effect to the primary flow in theline 72. Valve 70 is the primary expansion valve at the inlet to theheat absorption heat exchanger 66 to control the heat exchanger 66superheat. Expansion valve 99 could be used to do partial expansionbefore the flow enters the ejector in one mode and acts as the primaryexpansion valve on the high side for the basic cycle mode. Valve 84, 88,90 are on/off valves.

There have been a number of prior art proposals wherein the ejectorneedle has a fully closed/seated condition blocking flow through themotive nozzle. FIG. 3 shows one such example based upon theconfiguration of U.S. Pat. No. 7,178,360. In this situation, the needle132 has a main cylindrical portion 150 and a compound tip portion havinga proximal portion 152 at relatively shallow angle and a distal portion154 converging to the actual tip 156. The motive nozzle convergingportion also has a compound angle with a relatively steep proximalportion 160 leading to a relatively shallow distal portion 162 which, inturn, leads to a divergent surface 170 along the divergent portion 108.The exemplary portions 152 and 162 may have similar angles so as tosealingly mate in the closed condition.

SUMMARY

One aspect of the disclosure involves an ejector comprising: a motiveflow inlet; a secondary flow inlet; an outlet; a motive flow nozzlehaving an outlet; a primary flowpath from the motive flow inlet throughthe motive flow nozzle to the ejector outlet; a secondary flowpath fromthe secondary flow inlet to the ejector outlet, merging with the primaryflowpath at the motive nozzle outlet; a control needle shiftable along arange of motion between a first condition and a second condition andseated against the motive nozzle in the second condition. The needlecomprises: a main shaft; a tip; a first portion converging toward thetip; and a shoulder portion between the first portion and the main shaftand seated against the motive nozzle in the second condition andconverging toward the tip at a greater angle (θ₁; θ₁₋₂) than an angle(θ₂; θ₂₋₂) of the first portion.

In one or more embodiments of any of the foregoing embodiments: theshoulder portion angle (θ₁) is 15° to 75°; and the first portion angle(θ₂) is 5° to 60°.

In one or more embodiments of any of the foregoing embodiments: theshoulder portion angle (θ₁₋₂) is 75° to 115°; and the first portionangle (θ₂₋₂) is 5° to 60°.

In one or more embodiments of any of the foregoing embodiments, theshoulder portion angle (θ₁) is 10° to 30° greater than the first portionangle (θ₂).

In one or more embodiments of any of the foregoing embodiments, theshoulder portion angle (θ₁₋₂) is 5° to 80° greater than the firstportion angle (θ₂-₂).

In one or more embodiments of any of the foregoing embodiments, a throatof the motive nozzle has clearance relative to the needle in the secondcondition.

In one or more embodiments of any of the foregoing embodiments: themotive nozzle is made of stainless steel; and the needle is made ofstainless steel.

In one or more embodiments of any of the foregoing embodiments, theneedle comprises a transition section between the first portion and thesecond portion and being closer to cylindrical than the first portionand the second portion.

In one or more embodiments of any of the foregoing embodiments, themotive nozzle is a convergent-divergent nozzle.

In one or more embodiments of any of the foregoing embodiments, theejector further comprises: a mixer comprising a convergent portion atleast partially downstream of the motive nozzle; and a divergentdiffuser portion downstream of the convergent portion.

In one or more embodiments of any of the foregoing embodiments, a vaporcompression system comprises: a compressor; a heat rejection heatexchanger coupled to the compressor to receive refrigerant compressed bythe compressor; the ejector; a heat absorption heat exchanger; and aseparator having: an inlet coupled to the outlet of the ejector toreceive refrigerant from the ejector; a gas outlet; and a liquid outlet.

In one or more embodiments of any of the foregoing embodiments, a methodfor operating the system comprises: compressing the refrigerant in thecompressor; rejecting heat from the compressed refrigerant in the heatrejection heat exchanger; passing a flow of the refrigerant through theprimary ejector inlet; and passing a secondary flow of the refrigerantthrough the secondary inlet to merge with the primary flow.

In one or more embodiments of any of the foregoing embodiments, a methodfor operating the ejector comprises: driving a motive flow along theprimary flowpath; and shifting the needle to the second condition so asto stop the motive flow.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a prior art ejector refrigeration system.

FIG. 2 is an axial sectional view of a prior art ejector.

FIG. 3 is an axial sectional view of an end of a prior art needle.

FIG. 4 is an axial sectional view of a needle.

FIG. 4A is an enlarged view of a tip region of the needle of FIG. 4.

FIG. 5 is an axial sectional view of an ejector including the needle ofFIG. 4 in an open condition.

FIG. 5A is an enlarged view of a motive nozzle region of the ejector ofFIG. 5.

FIG. 6 is a view of the motive nozzle region in a closed condition.

FIG. 7 is an enlarged axial sectional view of a tip region of analternate needle.

FIG. 8 is an enlarged axial sectional view of the needle of FIG. 7 in aclosed condition in an ejector motive nozzle.

FIG. 9 is an enlarged axial sectional view of a tip region of yetanother alternate needle.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 4 shows an alternative needle 200 extending from a proximal end 202to a tip 204. Near the proximal end, the needle may have a mountingfeature 206 (e.g., an external thread) for mounting to an actuator. Theexemplary needle has a main section 210 along which the outer surfaceportion 212 is cylindrical (e.g., a circular cylinder of diameter D₁).At a downstream end of the section 210 there is a convergent shoulderportion 214 (FIG. 4A) along which the outer surface 216 converges towardthe tip 204 at an angle θ₁ (a half angle of the cone being half ofthis). There is thus an annular transition 218 between the sections 210and 214 and their associated surfaces 212 and 214. Similarly, at adownstream end of the section 214 is a section 220 along which theexterior surface portion 222 converges towards the tip at a shallowerangle than the surface portion 216. FIG. 4A shows this angle as θ₂.Again, this leaves an annular junction 224 between the section 220 andsection 214 and their associated surfaces 222 and 216.

FIG. 5A shows the needle in a relatively retracted condition/position. Ayet further retracted condition may be possible. In the FIG. 5Acondition, the tip 204 is approximately at the throat 240 of the motivenozzle 242. The exemplary throat is formed as a short cylindrical areabetween a convergent surface 244 upstream and a divergent surface 246downstream. The exemplary divergent surface 246 extends at a shallowangle to the outlet 110. The exemplary convergent surface 244 is at aslightly greater angle (θ₃ of FIG. 6) chosen to mate with the surface216 in a closed condition discussed below. The exemplary motive nozzle242 is formed as an insert into a body assembly and carries a needleguide 250 (e.g., at a step or discontinuity in the surface 244).

FIG. 6 shows the needle further inserted into a closed condition whereinthe needle tip 204 is concentrically within the divergent section of thenozzle formed by the surface 246. In this closed condition, the surface216 abuts a terminal portion of the surface 244 to close/seal the motivenozzle. The outer diameter D₂ (FIG. 4A) at the downstream end of thesurface 216 may be slightly smaller than the corresponding diameter ofthe nozzle at the throat 240 to allow clearance and avoid sticking Forexample, the outer diameter D2 could be 1 to 5% smaller than thecorresponding diameter of the throat so as to provide a clearance fitand yet avoid sticking of the needle into the throat upon actuationunder pressurized conditions.

In use, the closing of the ejector may serve the role of the solenoidvalve 88 of the FIG. 1 system, thereby allowing elimination of suchvalve.

Exemplary θ₁ is 40°, more broadly, 30° to 50° or 15° to 75°. Exemplaryθ₂ is 24°, more broadly, 20° to 30° or 5° to 60°. An exemplarydifference between θ₁ and θ₂ is at least 2°, more particularly at least5°, more particularly, 10° to 30° or 10° to 20°. Exemplary θ₃ is thesame as θ₁ (e.g., within 1° thereof). Relative to the FIG. 3 prior art,the change in taper may be relatively rearward on the top and allow arelatively low angle θ₂. It is better to have double taper at the backof the needle tip as it allows for better flow control by having a finerneedle tip (smaller angle) used to control a typical 2-phase sonic flowconditions that could exist at the throat. Sharp angle changes (as shownby larger sealing angles) near the throat could lead to eddy formationnear the throat that could lead to shocks in the divergent section ofthe motive nozzle leading to energy being lost in the form of heat.

FIG. 7 shows a needle 300 which may be otherwise similar to the needle200 of FIG. 4. The main section surface is still shown as 212 and thetip is still shown as 204. The overall tip region may differ from thatof the needle 200 in one or more of several aspects. A first exemplaryaspect is the angle θ₁₋₂ of the surface 316 of a shoulder 314 relativeto the angle θ₁ of the surface 216 of FIG. 4A. In this exemplaryembodiment, angle θ₁₋₂ is larger than that illustrated for angle θ₁.

A second illustrated difference is the presence of a step discontinuity315 (e.g., shallower than either adjacent section) between the surface322 of the section 320 and the surface 316 when compared with theintersection of the surface 222 and the surface 216. The exemplarydiscontinuity in the form of a straight section 330 having a circularcylindrical outer surface 332 and respective junctions 334 and 336 withthe surfaces 316 and 322. An exemplary length L_(S) of the surface 332is at least 0.01 inches (0.25 mm), more particularly, an exemplary 0.04inches to 0.2 inches (1 mm to 5 mm) or 0.5 mm to 10 mm.

Exemplary values for θ₂₋₂ are similar to those given above for θ₂. Anexemplary value for θ₁₋₂ is 90°, more broadly, 75° to 115° or 15° to145° or 45° to 120°. An exemplary difference between θ₂₋₂ and θ₁₋₂ is atleast 2°, more particularly at least 5°, or 40°-70°, more broadly,5°-80°.

FIG. 7 shows the needle 300 in a seated/closed condition with at least aportion of the section 336 accommodated in the throat of the nozzle.FIG. 8 shows that there may be angular mismatch between the angle θ₁₋₂and the corresponding angle θ₃₋₂ of the convergent portion of the motivenozzle. The exemplary θ₃₋₂ is similar to exemplary θ₃. This mismatchhelps with a better (tighter) sealing of the flow.

In yet alternative embodiments, θ₂ or θ₂₋₂ may go to an exemplary 180°with the associated surface portions being radial. The angels may evengo beyond radial. In alternative implementations with such a radialsurface or of the shallower surfaces, one or both exemplary surfaces maybe formed by separate members carried by the needle or by a main portionof the motive nozzle. FIG. 9 shows a needle 400 which may be otherwisesimilar to the needle 300 of FIG. 7. Along the straight section 330, theneedle carries a ring 420. The exemplary ring 420 is nested up againstthe junction 334 with the surface 316. The outer diameter (OD) of thering 420 is less than the main section diameter D₁. A downstream surface422 of the ring 420 forms a sealing surface for engaging to seal againsta fixed surface in the closed condition. An exemplary fixed surface isan upstream-facing surface 432 of a ring 430 inserted within the throatof the nozzle main body to, in turn, form a functional throat of thecombination of the main body and ring. Thus, the exemplary surfaces 422and 432 are essentially radial. Such a radial surface may be easier tomachine. It may also be easier to machine by placing it on separatemembers (the rings). Also the use of separate members allows forselection of ring materials to provide desired sealing properties whilenot changing material properties of remainders of the needle and thenozzle body.

Exemplary ejector materials and manufacture techniques may be thoseconventionally known in the art (e.g., casting and/or machining fromvarious metals and alloys, typically stainless steels). Use maysimilarly mirror use in the art with, in particular, use includingactuating the ejector to fully close off flow therethrough in theabsence of a separate valve.

Although an embodiment is described above in detail, such description isnot intended for limiting the scope of the present disclosure. It willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. For example, details of theparticular refrigeration system in which the ejector is to be used mayinfluence details of any particular implementation. Accordingly, otherembodiments are within the scope of the following claims.

What is claimed is:
 1. An ejector comprising: a motive flow inlet (40);a secondary flow inlet (42); an outlet (44); a motive flow nozzle (242)having an outlet (110); a primary flowpath from the motive flow inletthrough the motive flow nozzle to the ejector outlet; a secondaryflowpath from the secondary flow inlet to the ejector outlet, mergingwith the primary flowpath at the motive nozzle outlet; a control needle(200; 300; 400) shiftable along a range of motion between a firstcondition and a second condition and seated against the motive nozzle inthe second condition, wherein the needle comprises: a main shaft (210);a tip (204); a first portion (220; 320) converging toward the tip; and ashoulder portion (214; 314; 422) between the first portion and the mainshaft and seated against the motive nozzle in the second condition andconverging toward the tip at a greater angle (θ₁; θ₁₋₂) than an angle(θ₂; θ₂₋₂) of the first portion.
 2. The ejector of claim 1 wherein: theshoulder portion angle (θ₁) is 15° to 75°; and the first portion angle(θ₂) is 5° to 60°.
 3. The ejector of claim 1 wherein: the shoulderportion angle (θ₁₋₂) is 75° to 115°; and the first portion angle (θ₂₋₂)is 5° to 60°.
 4. The ejector of claim 1 wherein: the shoulder portionangle (O_(f)) is 10° to 30° greater than the first portion angle (θ₂).5. The ejector of claim 1 wherein: the shoulder portion angle (θ₁₋₂) is5° to 80° greater than the first portion angle (θ₂₋₂).
 6. The ejector ofclaim 1 wherein: a throat of the motive nozzle has clearance relative tothe needle in the second condition.
 7. The ejector of claim 1 wherein:the motive nozzle is made of stainless steel; and the needle is made ofstainless steel.
 8. The ejector of claim 1 wherein: the needle comprisesa transition section (330) between the first portion and the secondportion and being closer to cylindrical than the first portion and thesecond portion.
 9. The ejector of claim 1 wherein: the motive nozzle isa convergent-divergent nozzle.
 10. The ejector of claim 1 furthercomprising: a mixer comprising a convergent portion at least partiallydownstream of the motive nozzle; and a divergent diffuser portiondownstream of the convergent portion.
 11. A vapor compression systemcomprising: a compressor (22); a heat rejection heat exchanger (30)coupled to the compressor to receive refrigerant compressed by thecompressor; the ejector of claim 1; a heat absorption heat exchanger(64); and a separator (48) having: an inlet (50) coupled to the outletof the ejector to receive refrigerant from the ejector; a gas outlet(54); and a liquid outlet (52).
 12. A method for operating the system ofclaim 11, the method comprising: compressing the refrigerant in thecompressor; rejecting heat from the compressed refrigerant in the heatrejection heat exchanger; passing a flow of the refrigerant through theprimary ejector inlet; and passing a secondary flow of the refrigerantthrough the secondary inlet to merge with the primary flow.
 13. A methodfor operating the ejector of claim 1, the method comprising: driving amotive flow along the primary flowpath; and shifting the needle to thesecond condition so as to stop the motive flow.